Exfoliated graphene or single layer graphene, by any known exfoliation methods, which is submerged in an aqueous solution or medium, has a tendency to bind with neighboring graphenes to form graphitic nanomaterials. In some manufacturing aspects, graphitic nanomaterials are less desirable than graphene because graphene possesses better mechanical, electrical, and physical properties to name a few.
Conventional techniques for dispersion of graphene includes a method of producing graphene dispersion by oxidizing graphite using a strong acid into graphite oxide which is readily exfoliated and dispersed in an aqueous solution. This is then reduced thermally or chemically to a graphene nanostructure. These methods are generally weakening the interlayer bonding force with the introduction of oxygen groups and increase in the lattice spacing that will lead to easy exfoliation by sonication. Introduction of polymer substances between the interlayer for the same purpose also have been reported in the literature or well known. However, in the case where the solvent system or exfoliation medium is changed, an additional complicated treatment process needs to be performed. These methods would cause severe damage to the graphene structure due to highly acidic nature of the solvent and requires high temperature processing followed by reduction. This method is also time-consuming. Therefore, a novel method of dispersing graphene nanomaterial into the host material needs to be developed; and such method should be compatible with a variety of aqueous solutions, polymers, or the like.
U.S. Pat. No. 8,691,179 B2 by Kim et al. discloses a method for fabricating graphene sheets or graphene particles under supercritical condition. The exfoliation is enhanced in the supercritical condition by an external source of sonication. Moreover, Kim et al. cite the publication “Facile synthesis of reduced graphene oxide in supercritical alcohols and its lithium storage capacity” by Nursanto et al. in Green Chemistry, 2011, 13, 2714-2718, which discloses that the dispersion method is carried out externally by using an ultrasonic means toward a reactor, and the reaction is then immersed into a molten potassium-sodium-calcium salt based bath.
One major disadvantage of using the external source to generate the sonic wave is that it cannot be efficiently used in a dynamic fluid condition. Especially in a high throughput industrial environment, the required energy density and residence time will not be sufficient. The external sonic wave source dependent cavitation technologies will also suffer from a number of other drawbacks. The diminishing effect of the sonic wave away from the source and the cavitation efficiency due to the vessel size are some to name. Hence, it is beneficial to alleviate the shortcomings with the multiphase fluid dynamic generated supersonic assisted dispersion of present application.